Flaws in the new Leica M8 spark colorful debate.
Leica's long-awaited 10.3MP M8 ($4,800, street price, body only) went on sale earlier this month, just days after most magazines (including Popular Photography and Imaging) and online reviewers got their final production samples for testing. Shortly thereafter, at least one major web-reviewer posted his positive review of the camera without mentioning a serious image quality flaw that had reared its head during field tests -- apparently doing so at the request of Leica. Another reviewer openly admitted that image quality problems with the camera were forcing him to postpone his review until Leica had time to resolve the problem. This situation sparked two debates that have been raging on our forums and throughout the photographic community for the past few days. First, is the problem with the Leica M8 serious enough to warrant a total recall of all shipped and sold cameras? And second, should any truly "objective" product reviewer withhold potentially damaging information on a product in order to give the manufacturer time to fix it?
Editor's note: This article was originally published on Nov. 15, 2006, and reflects the state of affairs with the Leica M8's sensor sensitivity issues at that moment in time. On Nov. 25, 2006, Leica issued a statement that it had decided to offer a set of two free IR/UV filters to fix the IR sensitivity issue. Other problems are also dealt with in the following release, including a factory fix of cameras experiencing banding and ghosting problems. Read our follow-up here.
The first question is harder to answer than the second, and since there has been much speculation and misinformation regarding the problem, we decided to reveal some of our own findings now and give Leica a chance to comment on the cause of the problem and its proposed solutions. According to a spokesman, the company will not recall the camera, but plans to address the problem by the end of November through an accessory filter (which could cost up to $150, based on street prices of comparable ones) and firmware adjustment for digitally coded lenses (that's at least an additional $100 for older lenses).
What does the image quality problem look like? As we discovered in our field tests, dark black hair and many black fabrics may be surprisingly rendered in shades of purple or maroon instead of black. This is not limited to materials illuminated by studio strobes or hot lights, but will occur in a wide variety of lighting conditions, including daylight. However, until the photo is taken, it's not easy to predict whether or not an outfit or hairdo will exhibit this purple or maroon cast, and there's no way to set the camera color to limit the effect without changing the appearance of normal black tones. Other current digital cameras and DSLRs (except for those designed for use in IR photography) do not exhibit this problem. (For comparison photos taken with the Leica M8 and Nikon D2Xs, as well as other examples of the purple cast, click here).
Shooting in RAW DNG format won't fix this problem either (although it offers other benefits that we will highlight in our Certified Lab Test and review of the camera as soon as it's completed). There is no way to set the excellent Capture One LE Raw conversion software that ships with the M8 to automatically adjust problem areas in an image without skewing the color of blacks that reproduced properly. Currently, the only way to fix the problem when it occurs is to manually select and color correct it using image retouching software -- a time-intensive solution that few will find satisfactory, especially after purchasing a $5,000 camera.
To find out the exact cause of the problem, and what Leica plans to do about it, we asked Gero Furchheim, Division Manager Corporate Communications, Leica Camera AG, Solms, Germany.
His response begins on the next page.
Gero Furchheim, Division Manager Corporate Communications, Leica Camera AG, responds to concerns about the Leica M8 digital rangefinder:
The glass cover of the image sensor of the LEICA M8 is a combination of IR barrier filter and specially coated protective glass. The transmission in the red and infrared region of the spectrum can be controlled by the layer thickness of this filter. The comparatively small thickness we have chosen has proved ideal in the case of the LEICA M8 which is a very compact system. The short back focal length is the base for the compactness and the high quality of the standard and wide-angle lenses. Anyhow the resulting oblique angle of the incident light on the sensor requires special adaptations of the filter.
Absence of color fringing / Image Resolution
Due to the particularly thin layer, disturbing color fringing at the corners of the image is avoided. This phenomenon, which is also known as astigmatism and is frequently encountered with digital SLR cameras, is not a problem for the LEICA M8 due to the thin glass cover on the image sensor. This feature, plus the particularly high imaging quality of Leica M lenses, is the reason for the high corner-to-corner image resolution.
Rendering of black synthetic fibers
The elimination of color fringing and the improvement of image resolution have the side effect of higher IR sensitivity. Some synthetic textiles are therefore rendered in an artificial-looking purple color.
If the higher IR sensitivity has a disturbing effect in certain applications, e.g. fashion photography, LEICA Camera AG offers its customers a special IR barrier filter. This is screwed on in front of the lens and is an ideal combination of IR, UV and protection filter.
The use of the additional IR filter in front of the optical system has big advantages as the filter does not create reflections inside the optical system and thus enables the reproduction of finest tonal values even in shadows.
The filter is supplied as accessory with a special firmware adjustment which will be available shortly after the planned market launch of the camera at the end of November 2006.
The IR/UV filter is only suitable for use with digital M cameras and 6-bit coded lenses.
(Furchheim later added the following clarification: The IR filters do not generally require a 6 bit coded lens as I wrongly stated in my last message. We only recommend that lenses are 6 bit coded in the case of wide-angle lenses from 16 to 28mm to eliminate possible colour shifts.)
The high IR transmission may also be a creative advantage for applications in the infrared photography.
As clearly noted by Gero, the cause of the problem stems from the use of a thin IR cutoff filter (located between the Kodak-manufactured sensor and the rear lens element, see photo). Leica apparently chose a 0.5mm thick filter (mentioned in other press material) to prevent astigmatism and color fringing that might occur with a thicker IR filter. It should also be noted that the Leica M8 lacks an optical low pass filter (OLPF) used on most other digital cameras to prevent moiré patterns in highly detailed areas (more on this here). Forgoing the low-pass filter actually helps improve the resolution of the camera, albeit at the cost of increased moiré patterns.
Why don't thicker IR cutoff coatings -- and additional OLPFs -- cause noticeable color-fringing problems with digital SLRs such as the similar-priced Nikon D2Xs? The difference in the distance between the rear lens element and the sensor is the key. The Leica M8 lacks a flip up mirror required by a DSLR to redirect light to the viewfinder, but instead uses a rangefinder located to the side of the lens to aid composition. This arrangement has allowed Leica engineers to design a thinner camera body with smaller lenses for its famous line of 35mm film cameras, resulting in a far shorter distance between the rear lens element and either 35mm film or an imaging sensor. However, this shorter distance exacerbates problems with CCD or CMOS sensors, as rays of light coming in from the corners of the lens are at an oblique angle to the pixels and may not be detected without the help of microlenses located on each pixel. (For more information on this topic, click here.)
The Kodak sensor used in the M8 has specially offset microlenses located towards the edge of the sensor that optimize its sensitivity to angled light. A good illustration of this is found here.
Leica failed to mention that dark black hair and other black items (besides synthetic textiles) might also be problematic. And high IR sensitivity has been known to cause skin defects hidden below makeup or veins below the skin to appear in photos, although we have yet to test for this problem in the M8. However, Leica assured us that the increased IR sensitivity will not affect the camera's white balance system.
The solution Leica has proposed -- an optional IR filter for digitally coded lenses -- may not go over well with customers. Apart from colored filters for black-and-white photography, most Leica shooters shy away from optical filters or even protective UV filters, having already gone the extra mile to purchase some of the sharpest (and most expensive) lenses available. To use the M8 for, say, street or fashion photography, you'd need to buy a separate IR cutoff filter for each lens (at an estimated price of $100 to $150, given current street prices for third-party IR cutoff lenses), plus pay at least $100 per older M lens to have it digitally coded to work optimally with the M8.
On the bright side, the M8 could be a useful camera for capturing IR images (using opaque IR filters to block visible light) due to its increased IR sensitivity. But forget hand holding the camera or using it for IR street photography, as the built-in IR cutoff filter forces you to use longer exposures, higher ISOs, and even a tripod to get a good exposure. There are far cheaper and more sensitive solutions available for IR photography, including Fujifilm's new S3 Pro UVIR DSLR (see our Field Test).
The bottom line? Leica should have been aware of this problem before the camera shipped, as the selection of the thin IR cutoff filter was made as a compromise in the engineering phase for a reason. Is the discoloration a significant image-quality problem, and is Leica's solution acceptable? Potential Leica buyers will decide with their wallets. But the problem has definitely sullied the "first impression" of what might otherwise be a great camera. As a result, Leica should consider throwing in an IR cutoff filter for free whenever a lens is sent in to be digitally coded, or in the box with the newest coded lenses.
As for holding back damaging information in a claimed "impartial" test report? That's unethical when a product is already being sold and has certainly raised some credibility questions. Better to hold back the review for a short time and report on the manufacturer's response than to put out a positive review. In the past, we have been given pre-production samples to analyze, and give our first impressions of these in our "First Look" or "Hands On" reviews. Under those circumstances, we may give feedback to the manufacturer regarding problems or flaws and hope they rectify them by the time the product is released. Once a product ships or the manufacturer supplies us with a final production sample, we will test key features including (but not limited to) image quality, AF performance, speed, burst rate, and viewfinder magnification and accuracy and report our findings, whether positive or negative. After all, our loyalty is to our readers, not the manufacturer.
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